Platelets and Coagulation Flashcards
Describe the platelet number in general terms?
Formula for platelet # estimation.
Average # platelets in 10 fields x 20,000= #/uL
What two dog breeds usually have lower platelets numbers?
greyhounds
Cavalier King Charles spaniels
Describes the levels of platelets for mild, moderate, severe thrombocytopenia?
- Mild® 80,000-100,000/uL (marrow dz or consumption)
- Moderate® 40,000-80,000/uL (marrow dz/consumption)
- severe® <20,000-30,000/uL (marrow dz or destruction)
What is the main clinical sign of thrombocytopenia?
subcuntaneous/mucosal bleeding
What are the main classification of the causes of thrombocytopenia?
- peripheral
a. increased destruction
b. increased consumption
c. abnormal distribution - Bone marrow problem: decreased production
If an equine has thrombocytopenia and a bone marrow aspirate was taken, what is the likely diagnosis?
neoplasia
What does the picture show? What is it an appropriate response to?
Megakaryocytic hyperplasia-appropiate response to thrombocytopenia
What hematology abnormality does bracken fern posioning in cattle cause?
thrombocytopenia- disrupt production in the bone marrow
What infection causes cyclic thrombocytopenia and is known to infect platelets?
Anaplasma platys
A patient comes in 3-10days after being vaccinated with a modifed-live vaccine for surgery. What hematology index will be low? Should we pocede with surgery?
thrombocytopenia- wait more than 2 weeks to do surery
What is the inclusion?
A dog presents with thrombocytosis and the blood film below. What is the likely cause?
neoplasia (tumor in platelet)- may be primary thrombocytosis from neoplastic disease
What are the secondary causes of thrombocytosis?
- Iron-deficiency anemia; blood loss iron deficiency anemia
- Hypercortisolemia
- Inflammation® typically chronic
- Vinca alkaloids
- Post-splenectomy
- Rebound:
- after severe acute hemorrhage;
- ending myelosuppression
- resolution of immune-mediated thrombocytopenia
What happens to platelets levels after a splenectomy?
increase (thrombocytosis)
If there is an platelet type bleeding but the platelet level is normal and coagulation is normal, what is the best test to perform?
BMBT
What are the minimum platelets levels for most species and horses?
most species 7-10 platelets/100x hpf
horses 4-10 platelets/100x
What are the acquire causes of thrombopathia?
- fibrin degradation products inhibit platelet function (DIC)
- Drugs
- NSAIDs (aspirin, acetaminophen, phenylbutazone)
- anesthetics
- Bronchodilators
- Calcium channel blockers
- Renal failure
- Hyperglobulinemia
- Plasma cell neoplasia (multiple myeloma)
- Chronic ehrlichiosis
- immune-mediated thrombocytopenia
What are the congenital causes of a thrombopathia?
- von Willegrand’s disease
- rare intrinsic platelet defects
What are the vitamin K dependent coagulation factors?
2 (thrombin), 7, 9, 10
What are two ways vitamin K can become deficient?
rodenticide toxicity
maldigestion
What is the vitamin K factor with the shortest half-life?
factor 7
What event in the coagulation cascade leads to the formation of a stable fibrin clot?
thrombin burst
What factor is activated to form cross-linked monomers of fibrin in the clot?
Factor 13
what are the important regulatory proteins of hemostasis?
-
Plasmin
- Degrades fibrinogen, fibrin, crosslinked fibrin
-
Antithrombin 3
- Inhibits thrombin, factor 10a, factor 9a, and others
-
Protein C with protein S
- Inhibits factor 5a, factor 8a
-
Tissue factor pathway inhibitor (TFPI)
- Inhibits factor 7a and factor 1
- Tissue plasminogen activator- catalyzes plasminogen®plasmin rxn
What coagulation factors are consumed when blood clots and lacking in serum? Is serum good to use for coagulation testing?
Factor 5 & 8
NO
What should the ratio of citrate:blood be for coagulation testing?
1:9
What is PT?
prothrombin time-measured extrinsic coagulaton cascade
- Time for fibrin clot to form in citrated-plasma after adding*:
- Tissue factor (thromboplastin)
- Ca
- A substitute for activated platelet phospholipid
What is PTT?
activated partial thromboplastin time- measures intrinsic cascade and common pathway
- Measures time for fibrin clot to form in citrated-plasma after adding
- A contact activator
- Ca
- Substitute for activated platelet phospholipid
What are the two common issues that can cause the PTT to be artifactually increased?
- delayed testing and/or warming of the sample
- low plasma to citrate (aka short filled tube or erythrocytosis)
What does an elevated fibrinogen indicate?
inflammation
How can you differentiate from platelet vs coagulopathy type bleeding? Can you use petechiation as a definitive difference?
platelets- small bleeds, mucosal hemorrhage/petechiation
coag- major, dramatic bleeding, involving organs sometimes, joint spaces, SQ, petechiae may be present-not deciding factor
Which of the hemophilias are sex-linked? What sex are they more common in?
Hemophilia A (F8) and B (F9)
males
What are the differntials for increased consumption of platelets?
DIC
microangiopathic dz
vasculitis/endocarditis
envenomation
What infectious disease is known to supress the bone marrow?
ehrlichia
What are drugs/toxins that can supress the bone marrow?
anticancer chemotherapy drugs
bracken fern
estrogen
What are the differentials that cause decreased bone marrow production of platelets?
immune-mediated/idiopathic
marrow-replacement-neoplasia/fibrosis
infectious dz
drugs & toxins
radiation
What are causes of secondary thrombocytosis?
redistribution
increased prodcuction-
Fe-def anemia
rebound
hypercotisolemia
inflammation
vinca alkaloids
post-splenectomy
rebound
Name three reasons for a prolonged BMBT.
- thrombocytopenia
- vascular defect
- thrombopathia
Differentials for acquired thrombopathia?
increased FDP
drugs
renal failure
hyperglobulinemia
Differentails for congenital thrombopathia?
von Willebrand’s dz
rare intrinsic platelet dz
What is the function of factor 12, HMWK, and PK?
kinin in inflammation-WBC attractacts & pain
complement activation
activation fibrinolysis
What do you add to the test tube for a PT test? What does a prolonged PT test indicate?
Add Ca, TFIII, susbstitute for activate platelet phospholipid
inhibition/def factor 7 or common pathway factors
What do you add to the test tube for a PTT test? What does a prolonged PTT test indicate?
Add- contact activator, Ca, substitute for activated platelet phospholipid
inhibition/def intrinsic/common pathway factors
What deficiency do you need to see prolonged ACT?
95%
If D-dimers normal, but elevated FDP- what does that indicate?
increased fibrinogenolysis
Why would there be decreased clearance of FDP and D-dimers?
hepatic failure
